all right, scholars. all right, let's move on. let's begin.

hey, what's the difference between a hot cup of coffee and a cold cup of coffee? temperature. we say temperature. what's that mean? something different at the atomic level, hot cup of coffee, cold cup of coffee. in the hot cup of coffee, there's more activity. the molecules are jiggling faster. they have more energy of motion. we got a name for energy of motion. what do we call it? - kinetic energy. - kinetic energy. there's more kinetic energy in the molecules in a hot cup of coffee than a-- you know that. that's what it means to say that something's hot, that it has more energy. we might say more thermal energy. more strictly speaking, we'll say more internal energy, more energy internal to the system. so there's much more internal energy in a hot cup of coffee than a cold cup of coffee. what's got more internal energy, a hot cup of coffee or an iceberg floating down at the antarctica? check your neighbor for an estimate. a humongous iceberg or a small hot cup of coffee: which has the more internal energy?

all the energy combined-- what would it be, gang? yeah, the iceberg is frozen. how many say the hot cup of coffee still has more kinetic energy of all those molecules and those zillions and zillions-- come on, no, it's the other way around, gang. [laughter] it turns out there's more internal energy in the humongous icebergs simply because there are more molecules jiggling, you know? add up all the energy, you're gonna get a greater amount, okay? but when we talk about the energy per molecule, we're talking about an idea that begins with t. try it. temperature. temperature, yeah. temperature has to do with the-- per molecule, okay? so the--per molecule in a hot cup of coffee is a lot more than a heat per molecule in a hunk of ice. isn't that true? yeah. so we see there's a--difference between temperature and total amount of energy. temperature is an average, energy per molecule, kind of, yeah. we measure internal energy or any kind of energy in joules, or in heat units calories.

calories and joules are same, same. what is it? 4.186 joules equals 1 calorie, something like that. but calories and joules are both a unit of energy. and temperature is measured in degrees. degrees--how hot something is has to do with number of degrees. and that's different all together. it turns out that number of degrees that the amount of temperature has to do with the kinetic energy of motion. well, usually, things when you heat them up, they expand. most things will expand when heated. liquids, gases, solids all expand. guess which expands more, a gas or a liquid for the same change in temperature? gas. well, it turns out the gas. i can take a balloon and hold it over a stove. you could see that thing grow. if i take a a gallon of water and hold it over a stove, you don't see it grow very much. it does. and how about solids, how do they expand compared to gases? not so much, but they expand nevertheless. so liquids expand because liquids expand when they're heated. you could make thermal meters. thermal meters. let me show you an example of one.

you might do this in the lab part of the class. you might have a glass tube like this. and in that glass tube, you have some mercury or some alcohol, colored alcohol. you have it in here, say, like that, okay? and it might come up to this particular level. now, what you do as you put that thermal meter, which is a hunk of glass about this long with a reservoir at the bottom. you put that in a bath of ice cubes that are melting, melting ice. when you do that, the temperature of this becomes the same as the temperature of this because the slow moving ice molecules or slow moving water molecules over here impart only a little energy to here, or if this is hotter, by the way, it would send energy this way and heat up the water, you know? you can't have you thermometer too big. how about you get a thermometer this big and you're measuring this much water? come on, who's measuring what, right? in fact, you know, people say a thermometer measures its own temperature. and that's true because any two things put together will come to the same temperature.

and that's what happens here. so at zero degrees, there'd be a certain elevation of the liquid in there. and you could take a little glass file and you could put a little mark there, if you're in the lab part of the course, and say that's the level that corresponds to this particular temperature of water. now take that ice out of there, and take the water and heat it up until its boiling. boiling water, okay? boiling water, what's the boiling water molecules do to that glass? bam, bam, bam, they're really hitting. they're hitting with a lot of kinetic energy. and they bang into the glass with a lot of kinetic energy. and what do the molecules on the glass do? they start banging too. what do they do to the neighbor? bang, bang, bang, it cascades right through. next chapter, we'll call that conduction, where the energy cascades with molecular impact, bang, bang, bang, right? and finally, what do you know about liquid in there? that stuff is being shaken too. and when it's shaken, what's that do? it climbs the tube. it climbs the tube. climbs, climb, climb, then it finally settles off and stops. and guess where you make a second scratch? one guess.

there. no, not down here. not up here. guess, gang. right here. you put a scratch right in there, okay? now, you got-- and you can call this the temperature of boiling water. and we can call that 100. we can call this scratch down here zero. now, we got to make 100 scratches evenly spaced. so we get a hundred grades, a hundred grades. do you guys know what the prefix a hundred is? what's a hundredth of a dollar? it's a cent. no, not a penny. a what? a cent. a cent, okay? so we call this a centigrade thermometer. centigrade, because 100 equals centi, huh? so we got a hundredth grade, a centigrade thermometer. so we measure these things in centigrade degrees. see what i'm saying? so if you take this and put this in some other bath of water, and the level comes up to the same, you know it has the same temperature as the initial one. so that's a centigrade thermometer. now, in america, we don't always use the centigrade thermometer. americans are a little bit more innovative,

a little bit more maybe off the wall sometimes. american type do this, repeat the same experiment. and what the american type does is the american type put us in here and gets a scratch there. and he doesn't have to call it zero. you call any number you want, really? so long as you make them all the same way. give me a number, a random. 32. all right, 32. you could call that 32, okay? i mean, what's so special about zero, yeah? now, you put this in the boiling water, in the 32, bang, bang, bang. now, you put it in boiling water, bang, bang, bang, we're really hitting, huh? or--climb up, scratch, if you want to put a hundred there. if you want to wimp out and put a hundred like everyone else does, go ahead. but let's suppose you say, "let's get off the beaten path." take any--give me a number, random, any number. 212. all right, 212. all right, 212. all right. now, what do we call that thermometer? an american thermometer, okay? [laughter] well, that-- and what we're saying is the boiling point of water is 212 degrees and the freezing point of water is 32 degrees, okay? now, here is the problem, gang. you got to cut up equal number-- you got scratches in there.

how many scratches are you gonna have between 212 and 32? and you can't do it. anyone got a calculator? nobody? anyone do it, maybe pencil and paper? how many scratches between here and here? this requires an arithmetic operation. it requires taking 32 away from 212. the two is all right, but look at the three. you got to subtract the three from the one. you got to do some carrying. [laughter] oh, let me tell you, gang. i've done it before. it's 180, 180. so you got 180 scratches. does anyone know what the prefix 1/180th is? -- a fahren, that's right. engineer types know that. that's a fahren. so we call this a fahrengrade thermometer, okay? ever hear of a fahrengrade? no. we don't call it fahrengrade thermometer because we named th thermometer after the man who invented the scale. in honor of him, we name it for him. so it's not a fahrengrade. does anyone know the name of that guy? james j? thermometer. [laughter] james j. heit.

mr. heit is the one that done that, so we call it a fahrenheit thermometer. do you believe in this? i'm just toying around with you guys over there, okay? but anyway, this is fahrenheit thermometer is measured in smaller degrees, in small degrees. you got 180 of those suckers in between freezing and melting, boiling point. in the celsius, you got 100-- it'll spread out more. so what's more accurate to the degree, fahrenheit or centigrade? fahrenheit. fahrenheit, you see, because in centigrade, you got to deal with more fractions. but fahrenheit has more spaces, finer tuning. so those are the two thermometers. then there's another that we'll take about when we get up to thermodynamics and that's called the kelvin scale. and the kelvin scale is named after some dude by the name of james j... - scale. - ...scale, you got it. you got it, all right. so we have those kinds of ways of measuring temperature, the average kinetic energy per molecule of things. here's a nice distinction between temperature and internal energy, or, loosely speaking, heat content. this used to bother me when i was a kid.

you know those 4th of july sparklers? you light them and they-- [makes noise] --and all those white hot sparks going out. and do you know whathe temperature of those sparks are? -- more than 1,000 degrees celsius, more than 1,000 degrees. is that hot or cold? - hot. - cold. "h," no, no, no, begin with a "h." [laughs] hot, okay. those are hot sparks, gang, over 1,000 degrees celsius. ever see little kids with those little sparks at home, like, hey, look at sparkler, honey, that's gonna dance sparks bouncing off the kid's eyeballs and his cheeks and everything. and the kid-- does the kid scream? the kid's okay. and i said, "wait a minute. "the temperature of those sparks is white hot temperature, enormously high temperature, how come the kid ain't hurt?" and it has to do with the definition of temperature, proportional to energy per molecule. every molecule got a humongous amount of energy, but how many molecules in that little spark?

not so many. so what's the total energy of that spark? not so much. below the kid's threshold of feeling. so although the temperature is hot, the heat content, the internal energy of the spark is very low. later on, we'll do a similar thing. i'm gonna rub a balloon against my head, and i'm gonna tell y guys, this balloon got, like, thousands of volts. but we'll learn there that voltage is sort of like electrical pressures. it's energy per charge. not many charges, so not much total energy. with the sparkler, not many molecules, so not much total energy burning the face. so temperature and heat content or internal energy, two different things. and by the way, we got a definition for heat that departs from the commonplace definition you have on the outside. and that is we say that at is the energy that flows from one object to another by virtue of a temperature difference. so heat is always energy in transit. strictly speaking,

when the physic talks about heat, the physic is talking about energy in transit. total amount of energy, physic are talking about internal energy. and the energy per molecule, the physic are talking about an idea that begin with a-- check your neighbor. it begins with a "t," gang. try it. - temperature. - temperature, temperature. it's the difference between temperature which is measured in degrees and heat which is measured in calories or joules. got such thing? different things heat up different rates. you're at home, you get your stove. if it's an electric stove, red hot. you take a frying pan, take a frying pan, put it on the stove, turn around, come back, put your hand on the frying pan. oh, you burn yourself. tattoo city, honey. you have burned yourself.

take that same frying pan, this time, pour a little water in it. now, put the wat-filled frying pan on the stove, tu around, the telephone ring. [makes noise] "what's it--no, no, "i don't want any aluminum siding on my house. thank you anyway." boom. you come back later, a few minutes later, put your hand on the water, huh, - it's okay? - it's okay. it's okay? if you can do that, you can do that, it's okay. now, i got a question for you, which do you suppose has more internal energy? which has absorbed more heat, the frying pan empty or the frying pan with the water in it? think. i'm not asking which has got the higher temperature. i'm asking a different question. i'm saying, which has absorbed the most heat? and your neighbor says... -- what's the answer, gang? the water.

the water has absorbed more heat. but you know what? it's not as hot. the tempature is not so high. so some substances will absorb an awful lot of heat for only a small change in temperature. iron, put a little heat energy in it, whoop, the temperature soars. but water take a lot of heat energy to make the temperature higher. that has to do with temperatur being the translational, back-and-forth motion of the molecules. when you heat up iron, the little electrons in there start zapping back and forth, back and forth, make the molecules move back and forth. translational kinetic energy, that temperature goes up very quickly. but it turns out, when you heat up the water, that water is a funny little devil the. that water doesn't just shake back and forth. what the water does, it puckers in and out, in and out. and it gets into--look-- what's called, internal rotational states. and the hydrogen bonding makes them all fixed together so they won't shake so much, but they have the energy in a potential form. and so that doesn't drive the thermometer up very much at all.

so you can put an awful lot of heat in water, and the temperature goes up a little bit. we say water stores an enormous capacity of heat for small temperature rises. we're talking about specific heat. physics will say, "hey, water got a high specific heat," means it'll take in a lot of heat for a small temperature change. that's why you use water in your radiator in your car. what do you want the water to do in your car? you want it to absorb that heat energy from your car, so it doesn't melt, right? and so a little bit of water will absorb a lot of heat energy. and the temperature doesn't go right and boil away on you either. it turns out the water will absorb a whole calorie of heat energy for every gram. it only goes one temperature-- to one-degree temperature change, one celsius degree. specific heat of water, one calorie per gram degrees in celsius. so water, a big specific heat compared to other things. you can ach in aoven and take out with your bare hands an aluminum dish. the tv dinners, you've done that. you can't hold on it r a long time, but you can take it out quickly and put it down, then your hands are okay.

because it turns out, what? that aluminum dish has not absorbed as much energy for its high temperature change as something like water would. or when you're eating food, some foods you eat, you can eat very, very hot comfortably. there's not very much energy in there. in some foods, especially with the water, like the inside of pie filling, you eat it, and, ooh, you'll burn yourself, because that high temperature has an awful lot more energy in it than the--= than say something like the aluminum foil on a tv dinner, something like that. different things ha different specific heats. i know water has a high specific heat. i remember when i was a kid. when i was a kid, i grew up in the outskirts of boston. and in the wintertime, gang, it is cold. and upstairs, we had one radiator in the house, and that was in the bathroom. and the bedrooms are really, really cold. you had to get the heat from downstairs. it will come up by a process we'll call-- later call convection, okay? or we'll have to come a little bit from that radiator and migrate into the rooms. anyway, it was cold, and in cold nights, we had a way of getting through. what my mother would do is, downstairs in the kitchen, she would cook a great, big bucket of water. i mean, not a bucket but a great, big pan or what do you call it?

pail, you know what i'm talking-- a container, container, okay, a container of water. it would take a long time to heat that water up, gang, a long time to heat that water up. and she'd take that water and she'd pour it into a jug. and that jug was what we call the hot water bottle. and that jug was like a clay jug, and she'd fill it really hot-- i mean, really, really high. and you put your feet on it, you're gonna burn. so we put a towel on there. and you go upstairs and you put it in your bed, you put it at the bottom, and you put your feet on it. and we had an old adage, that if your feet are warm, you're warm, okay? when your feet get cold at night, you're sleeping on--you can-- that's tough city, okay? but if you put your feet on that hot water bottle, it's okay. and in the middle of the night, it gets so-- it's not quite so warm, you reach down, you take the towel off, and you put your feet right on the bare, and you get all through the night. it's okay. didn't know anything about physics then. but looking back, i could see water got an enormously high specific heat, meaning, an awful lot of calories in that jug of water. and those calories are delivered slowly and slowly through my feet. so it was kind of neat. so high specific heat for water.

the high specific he of water has to do with different climates throughout the world. here, i've got a globe here. let's take a look at this. go over to england. here's england right here. go to england on a summertime. how's the weather in england on the summertime, okay onot okay? -- begin with a o. it's okay. it's tolerable. but, honey, england doesn't really get very much sunshine. because if you keep your finger on england and turn the globe-- [makes sound] i can't do that now. you're over here in labrador. what's the climate like in labrador in the hudson bay, okay or not okay? - cold. - well, it's relative. it depends what you call okay, okay? but, honey, it is. begin with a c end with a d. - cold. - it's cold. it's very, very cold, cold climate there. but you know what? it's the same latitude as england. so why? england is surrounded by what?

begin with a w. - water. - water. and that water has a high specific heat. and that water is really heated up down here by the equator, isn't it? water is heated up down here all year round, right? and that water drifts north in what's called the gulf stream. i guess someone near the gulf must have named it, yeah? and that water drifts north. and how many will say, "oh, that water must cool off real quickly." no, no, no, that water don't cool out quickly. that water migrates right up through here and comes off here in the north atlantic and there it settles. and you know what? the water does cool down. conservation oenergy. to say the water cools down is to say something else gotta--wu. - warm up. - warm up, all right, yeah. see that, gang? so when the water cools, the energy got to go somewhere and so it goes to the ai and the winds at these latitudes are westerly, and the winds go this way and warms up all of england. but look at poor labrador over here or all these regions up here-- way up in here. that's up here. man, there's no water that's cooling off.

now, i will submit on this side of the hudson bay. you should have a better climate, a warmer climate than on this side of the hudson bay because the winds are going this way. same thing in san francisco. san francisco has palm trees. the same latitude is san francisco. here's washington, d.c. honey, the best they can do are cherry trees, okay? [laughter] no palm trees. the only palm trees in washington, d.c. are in the hotel lobbies, okay? right? but we have palm trees in san francisco, and why is that? same latitude, same amount of sunshine per unit area, see? but it turns out, what? we got the gulf stream-- not the gulf stream-- we've got the ocean out here. now that ocean, if that ocean in the wintertime cools down a little bit, what's the air do? you wu. - warm up. - warm up, okay? and if it blows this way, what's it hit? begin with a cal f-o-r-n-i-- so california is a much warmer place in the winter than east coast communities of the same latitude. ain't that neat, okay? in fact, any place that's surrounded by water

has just about the same temperature all year round. how about the best place in the world, right here? [laughter] that's hawaii, huh? the hawaiian islands, okay? the hawaiian islands about the same temperature all year round, but not only the hawaiian islands. iceland way up here has about the same temperature all year round, yeah. surrounded by water, okay? when it tends to be cold, the cooling water would heat it up. when it tends to be hot, the warming water will cool it down. so water acts as a moderator. aren't you glad that water has a high specific heat? yum, yum, itad to do with the world we live in, yeah? something else about water, kind of neat too. water is the only substance-- the only commosubstance that will expand when you change it from the liquid state to the solid state. did you guys know that? see, ice will float on top of wate why?

during the freezing, the ice must have puffed out. the ice puffs out. and why does the ice pufout? you guys ever see snowflakes? leave it after school today, and go out and catch a snowflake. let them-- [laughter] --fall on your sleeves, okay? if you got a black sleeve-- you look at the snowflake really carefully, "hey, son of a gun, the snowflake got six sides. "hey, this one got six sides too. "hey, they all got six sides. i wonder why." your friend said, "well, there's probably no reason for that. it's just characteristic of snowflakes." and what do you say? "hey, there got to be a reason." and the reason for the six sidedness of the snowflakes has to do with the way the h2o molecules pack together in their least energy configuration. and as they're all packed together and theyorm hexagons you see that in the textbook? and this is on page 263. and they form these hexagon structures with an open space in the middle. so you know what that means? a snowflake takes up more room in the snowflake form than if you melt it and turn it back to wate you turn it back to water, the molecules will caved in and occupy that empty spot.

it's like a brick building. a brick building occupies more space when it's in its constructed configuration than if you shake it so ha, you shake all the bricks and they cave in. the pile of bricks is less voluminous than the brick building was before it caved. same thing with ice, gang. so water forms an open structure in its crystalline form, and that's kind of nice. it makes ice less dense than water, and the ice will float. so you can go ice skating, gang. some people are kinda good at facts and figures. does anyone here know when it was that christopher columbus sailed for america? you probably don't be knowing that year. how many people happen to know the year from their history? can i have a show of hands? one, two, three, four, five, six, six, seven, eight scholars.

okay. it happened to be 1492, gang. do anyone happen to know when the declaration of independence was signed in the united states? it's a pticular date. some people have it engraved in their heads and some people say, "oh, i don't need to be knowing such thing." when was the declaration of independence signed? anyone know what year? have a show of hands. i wanna see you is. show of hands. well, we got almost half the scholastic class here. it turns out to be 1776. some of us are good for remembering figures and some of us aren't. let's try something different. the temperature at the bottom of lake supeor, new year's eve, 1900, does anyone in here happen to know what the temperature at the bottom of that lake was at that time? one, two, three, four, five, six, even less people than knew when the declaration of independence was signed. and what has happened-- the temperature happened to be, gang? say again?

- four degree celsius. - four degree celsius. you're right, four degrees centigrade, right. celsius, centigrade, same, same gang. that's right, right on. does anyone happen to know what the temperature at the bottom of lake tahoe? that's over a half kilometer deep. lake superior is almost half a kilomet deep. but lake tahoe in california, does anyone here happen to know the exact figure of the temperature of the bottom of that lake right now? one, two, three, all of the same hands. what's the answer, gang? four degrees. four degrees celsius, that's right, that's right, that's right. hey, outside the building here when i came in, there was a big puddle. does anyone happen to know what the temperature is at the bottom of that puddle outside right now? no, it a't four degree celsius. [laughter] no, no, no, no. it's not. the temperature of the puddle is the same as the temperature of the air outside, okay? they're all the same, but how about a deep body of lake, gang? do you know why the bottom of those lakes are four degrees celsius all year round all the time?

first of all, they're at latitudes where there's four-degree weather in the wintertime. so let me ask you a question. oh, you don't know about four degrees yet. four degrees. i got to tell you something about four-degree water. four-degree water is like dense or not dense? dense? - dense or dense dense? - dense dense. honey, four-degree water is the densest water you can get 'cause water has different densities at difrent temperatures. see, if you heat some water up, wouldn't the volume get more a more and more? you know that's true because if you put a pan of water on a stove and fill it brim-filled and then turn on the stove, what's the water gonna do, gang? beginning with o, f. - overflow. - erflow. the water is going to expand, see, okay? so the water, when it expands, it'll have more lume for the same weight, it will be what? less dense. so density depends on temperature. but it turns out ice got less density than boiling water. now, how come? because it forms all those open structures.

i'm going to make a graph here and this graph is volume, volume of water versus temperature. i'm gonna consider some ice water-- not ice, not solid ice-- ice water. and that ice water has a particular volume like this. now there are two things gonna happen when i heat the ice water. number one is, when you heat anything, the molecules will start jiggling faster, faster, faster and take up more room. so there's sort of an expansion, okay? we'll just say, as the temperature goes up, the volume increases. that's true of most everything that you heat up. it'll grow bigger and bigger the faster the molecules shake, okay? but something else happens with the water that doesn't happen with other fluids, other liquids. and what happens is those open-- it turns out in that zero-degree water, you got a whole lot of those open crystals, it's like a microscopic slush.

and that microscopic slush, when you start heating it, what does the slush do? [makes noise] it caves in. and when it caves in, does it take up more room or less room? less. less room. and so when you heat water, due to the microscopic slush that's in there starts caving in, the water starts to get down. and so you got two things going on, a cave-in as temperature increases, and an increase in volume as temperature increases. put them together, when you combine them, you get something like this. and right here, that's four degrees, four degrees above freezing hathe least volume. see that? and then above four degrees, it starts to go up. you still got some ice crystals crunching in there, but this part here has overtaken it and it goes like that. so you have this dip in the curve which turns out to be very interesting, very interesting. th dip in the curve has to do with the fact

that on these deep lakes like lake superior and lake tahoe, i don't care how cold the winter gets, gang, you're not gonna get any ice on those lakes. and let's see why. a shallow lake, yeah, but a deep lake, no. i've been up to lake tahoe and after that-- i've asked the people, "hey, how come you got no ice on the lake?" "oh, it's too deep. "go to lake donna down the road there, "you got plenty. you go ice skating there." you're not gonna skate in tahoe, gang. tahoe never freezes over. how come? 'cause it's too deep, which kind of begs the question, "well, how come too deep means it won't freeze?" so he says, "hey, i'm not a physics type. just keep moving, honey, okay?" but let's look in, we are physics types and we wanna see if there's a reason why that deep lake won't freeze. and it turns out it has to do with what we're talking about right now. let's take a look. here's the lake. okay, let me try this.

here's the lake. now let's suppose that lake is 10 degrees above freezing, so it's not gonna-- what's the temperature which freezing takes place, gang? - zero. - zero. okay, so if i'm gonna freeze some water, i got to bring it from 10 down to zero, yeah? okay, let's suppose out here, this is the air, let's suppose it's 50 degrees below zero. i mean, cold. and that cold air blows over the top of the lake, how many people think that cold air blowing over the top of the lake is gonna make the temperature at the surface go up? show of hands. good. nobody. how many say, that cold air will probably make the surface temperature go down? show of hands. well, almost every--like-- hey, we got everybody? does everyone think that? have you got 50-degree-below-zero air blow over you, you're gonna get colder, not warmer? isn't that remarkable? [laugh] come on you, gang, there's nothing remarkable about that. but i'll show you a remarkable consequence of that.

it turns to nine. we'll do it by incremental steps, nine degrees. the wind, eight, can you see that makes sense? where do we got to get to? zero, yeah? - zero. - okay. do anyone see something unusual here? let me ask you a question. if i take a rock and throw it in that lake, what's the rock gonna do? float. how many say, "oh, it will probably float"? [laugh] the rock is gonna sink, man. and why is the rock gonna sink? "well, that's characteristic of rocks, just to sink." come on, why does the rock sink? 'cause it's more dense than the water, right? how about this four-degree water? what's it gonna do, gang?

beginning with an s, end with an ink. sink. sink. sink to the what? bottom. the bottom. here's your four-degree water down here. what takes its place? beginning with a t. - 10. - 10. by now, it's february, okay? get the idea? honey, we're gonna need a long winter to get to that lake. but now it's march. how much time do we have? we get--the thing, you get the idea. [laugh] what happened at four, honey? by now, it's may.

people, it's may, we're running out of winter. you can't get a deep, deep lake to get all four degrees. before you can get any three-degree water, never mind zero. what are you gonna turn the whole lake to? four. and let's suppose we have like a big meteor hit or something and we get, like, no sunshine for about four or five years then we'd get something like this. you keep doing the same thing and pretty soon, after a couple of years of that, then it would all be four. honey, that's a lot of energy taken away by that cold wind. when you get the whole lake four degrees celsius, then and only then, that's the first three-degree water that lake has seen, gang. does it stay there or does it sink?

it stays there because what's down below is more dense. the lighter, the less dense will float on top of the more dense. that makes sense? watch. now we got zero-degree water. those of you who are sitting close today will see something that those in the back of the room might not see. but watch very carefully to what happens to the water at the top. [makes noise] do you see that? did you guys see that? did you see the crystals form? again. [makes noise] see, it's a little thicker? did you see those crystals form at the top? [makes noise] do you see now why ice forms at the top of a body of water? ain't that neat? so now you start to get some ice and the ice floats on top of the other water. do you see why you have to have-- although that only happens with the shallow.

you go up to lake tahoe and you take a saucer full of water, put it outside your motel room, come in and play checkers, half a game and go back there, boom, that water is solid ice. and you look out at the lake and it stays water all the time. now you'd be saying, "why?" the reason for those sort of things. how come then, like, glacier waters rapids, like some are-- is only about, like, four or five feet deep. say again, say again? how come some glacier waters like rapids is only about four or five deep. i know they're moving, but how come they don't freeze 'cause they're like ice, that's ice cold. how come moving water doesn't freeze? yeah, how come moving water doesn't freeze? well, sometimes moving water does freeze. you just usually see on the outside edges though, right by the land. you never see the whole thing freeze over. yeah. that seem like a pretty easy question to answer, doesn't it? wouldn't you expect your teacher to be able to be, "oh, the reason for that is blah, blah, blah." well, i don't think i can give you a good answer for that other than say that the crystals can't-- they're not a good answer. can we still be friends? [laugh]

oh, that did it? okay. try another question. give me one that i said i can answer. okay. hey, let's talk about this expansion and this expansion under different temperatures and everything. we got something here that's kind of neat today. ted, could you give me a hand? talk about low temperatures. ted has brought over here some liquid nitrogen. this liquid nitrogen is about 190 degrees below zero celsius, really, really cold almost 80 degrees above the absolute zero temperature. now, can we have a volunteer to jam their hand in there for about five minutes? [laughter] okay, nobody gonna do that, right? okay, let's show how the-- let's take the-- let's show how the volume of something will change. here's an air-filled balloon, gang. okay, what's gonna happen to the volume when it gets cold?

how many will say, "oh, it's gonna expand"? stand up. and what happens to the volume, gang? look at that. now, it's gonna start to warm up the air temperature. what happened to the volume? what happened to the volume when we bring it above air temperature? hang it a little closer, ted.

-- yeah. [laughter] let's try the flower. there's a flower ted found out in the ground. it's kind of nice and limp, right? kind of limp, isn't it? okay. so what happens is you slow those molecules down. why did it fizzle like that? yeah, why did it fizzle like that? what's going on? oh, gang, did you see such a thing? look at that, gang. if you stuck your hand in there and hit it against the table, would it do the same thing? yes, yes, can we have a volunteer, please? [laughter] unfortunately, it would, yeah. another one? right. would a pen break? you wanna try it? yeah. okay, ted's got a little-- let's see if i can do this. i did this a long time ago. what was that?

now, i got a friend of mine, his name is gerald walker who does something that i don't have the guts to do. gerald takes the stuff and drinks a little bit and blows out. i ain't gonna do that, gang. [laughter] ted is doing pretty good, yeah? guess who's got the courage of the two of us? come on, try one. here's where you get the bnta. what did you do? did you eat it? is it all right? did you put it in your mouth? what will you do is hold it. well, it isn't your tongue, put it over your teeth and then just blow over the top of it. i only drop, of course, i don't have any experience. i didn't say how you did that, ted. it will be-- you want me to-- oh, i have an extra one. do you want me to do it first? you do it first. let me look and see what you're doing. okay. you pick it up. yeah. [laughter] anyone hungry? i've got one more. we'll do this at the party, gang.

it's a little cool, yeah. that's why you don't stick it on your tongue for a long time but, again, the same story with the white hot spark, it's not real cold for a long time. here you go. thank you, ted. whole way, man. whole way. [laughter] okay. yeah, i've--how death defying-- going to be here. we got a penny. what do you suppose happened to the size of that penny that we put in here, gang? if you had some calibers, you measured the diameter, what would happen to the diameter when it's cold, get larger or smaller? smaller. smaller. they'll shrink, right? is that water warm after a while it's been out in the air? oh, it's not water. this is liquid nitrogen. yeah, liquid nitrogen. oh, darn. does it warm up though after? oh, yeah, it's warmed up. it's boiling. it's boiling right now.

that's what this stuff is. it's boiling right now. do you want to see if this gonna break, right? no. that's gonna be-- so that's a little real. now, do you want this back? we're gonna make our own. [laughter] copper is a very good conductor. does the-- so when we cool things, gang, they expand or they contract? question. isn't that plastic container? yeah. is it brittle? yes, it is very brittle, very brittle, yeah. see the frost in the outside? if you ever drop that, it will probably just crack. hey gang, i want to leave you with a question. when we cool things, they contract. right. when we heat things, they expand. if i heat this ring, get it really, really hot-- and i'm gonna do that next time. next time, i'm gonna put it under the blowtorch and i'm gonna get it really, really hot. would it become larger, smaller or stay the same?

let's suppose we did this as a test. i took the ring and let's suppose the ring right now will pass through the-- let's suppose the ball will pass through the ring. if i heat the ball up, will it still pass through the ring? no. that's elementary. i would insult you if i told you to think about that for a long time, right? we know the ball is gonna get bigger. and if the ball gets bigger, it will never get through the hole if it just barely makes it now. isn't that true? here's the question i got for you. the next time we come in, i'm not gonna heat up the ball. i'm gonna heat up the ring. and when i heat up the ring, will the ball be able to get through if it just gets through now? will the hole become larger, smaller or stay the same size when i heat the ring? think about that 'cause we got that for homework. hey, you know what?

you can do this as a test, experiment. take a ring off your finger, put it on the stove, get it hot. does the hole get bigger, smaller or stay-- and then jam it back in your finger and see. [laughter] no, no, not your finger, your kid sister's finger, all right? and see if the hole gets larger, smaller or stays the same and see if you can say hc for next time, gang, okay? homework? as a homework. catch you later, physics. [music] captioning performed by aegis rapidtext